This invention relates to a device for automatically controlling the timing of a driving mechanism such as a clutch or a solenoid in an apparatus such as a copier or a facsimile machine provided with a paper transporting mechanism.
With a driving mechanism such as a clutch or a solenoid, the time between receipt of a command and its actual execution is not zero and there is usually a delay of several milliseconds. For this reason, synchronism is lost due to such a delay in most apparatus with a transmission system using clutches and solenoids. In an electrophotographic copying machine, for example, a sheet of paper transported from a paper cassette by feed rollers is temporarily stopped at the position of timing rollers and is delivered therefrom to the photosensitive drum by the timing rollers which begin to rotate after a predetermined length of time but if the delay is large in the transmission of the clutch for driving the timing rollers, synchronism becomes unattainable and the front edge of the delivered sheet cannot come exactly to the designated position on the photosensitive drum.
Although previous attempts to overcome this problem included providing an adjusting means such as a timer for making a timing adjustment when the apparatus is assembled, the delays associated with clutches and solenoids are themselves known to change with time. In other words, even if synchronism is established at the time of the assembly of the apparatus, it is gradually lost with time and adjustments are required periodically.